1. Field of the Invention
The present invention relates to optical articles such as ophthalmic lens and, in particular, to a method and apparatus for hard coating the optical article to increase the abrasion resistance and enhance other physical properties of the optical article. The invention provides a continuous or semi-continuous method and apparatus for hard coating optical articles which is efficient and cost-effective wherein two carriages at a time are reciprocated separately on a conveyor in uncoated lens loading and coated lens unloading sections to provide from the loading section a carriage full of uncoated lens ready for hard coating and from the unloading section a carriage full of jigs for holding lens which carriage is ready for transfer to the lens loading section.
2. Description of Related Art
Lenses are used for a wide variety of purposes such as microscopes and other optical instruments as well as ophthalmic lenses used for eye glasses. While the present invention involves a method and apparatus for hard coating any type optical articles or lenses, the following discussion will be directed for convenience to ophthalmic lenses.
Polymeric materials (e.g., plastics) have become the material of choice for ophthalmic lenses and have replaced the more traditional glass lenses for a number of reasons. Plastic is lighter than glass and there can be great reduction in the weight of the optical product. Plastics also may be provided in a wide range of fashionable colors and gradient-density tints and production techniques have improved so that plastic lenses can be manufactured at high rates and in a more automated fashion than glass lenses. Polymeric materials also offer great improvement over glass in terms of impact resistance and high refractive index. In general, plastic lenses are now the lenses of choice in the industry.
Plastic lenses may be manufactured in a variety of ways by individual casting techniques as well as injection molding processes. Regardless of the method of manufacture, however, the plastic lenses typically require a hard coating to increase the abrasion resistance of the plastic lens. The hard coating is typically applied by dipping the lens in a liquid hard coating solution and the coating is then cured by chemical cross-linking. U.S. Pat. No. 3,956,540 to Laliberte et al. entitled “Method of Coating Articles” is directed to a method and apparatus for applying a synthetic resin coating of predetermined thickness to ophthalmic lenses. Basically, the lenses are grouped and moved along a conveyor and are subjected to an ultrasonic cleaning. The cleaned lenses pass to a destaticizing station and then to a coating station where a dip tank is rapidly raised to immerse the lenses in the solution and the tank is then lowered at a controlled rate to provide a coating of the desired thickness on each lens in a single operation. The above patent is hereby incorporated by reference.
U.S. Pat. No. 5,750,060 to Maus et al. is directed to plastic injection-compression multi-cavity molding of flash-free improved-cleanliness thermoplastic spectacle lenses which are suitable to be robotically dip coated. A molded-on tab with each pair of lenses is specially suited for manipulation by a robot and the procedure produces micro-clean hard-coated paired molded lenses made entirely within a single continuous cleanroom air enclosure surrounding the lenses without any human operators therein. This patent is also incorporated herein by reference.
Regardless of the method used for making ophthalmic lenses and whether or not the lenses are single lenses or made together with tabs, there still exists a need for an automated cost-effective method for hard coating the lenses. The hard coating method and apparatus should be capable of being used with little or no human intervention and provide an efficient and reliable method for hard coating the lenses.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a batch, semi-continuous and/or continuous method for hard coating optical articles such as ophthalmic lenses which method is cost-effective and reliable and may be automated so that little or no human intervention is required.
It is another object of the present invention to provide an apparatus for batch, continuous and/or semi-continuous hard coating of optical articles such as ophthalmic lenses which apparatus is cost-effective and reliable and requires little or no human intervention to operate the apparatus.
In another object of the invention hard coated optical articles such as opthalmic lenses made using the method and apparatus of the invention are also provided.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.